1. Field of the Invention
The present invention relates generally to the field of crop breeding. More specifically, the present invention relates to a method for controlling the ratio of proteins/lipids in crop seeds using antigenes, and new plants with high oil or protein productivity produced thereby.
2. Description of the Related Art
It has been known to increase the protein or lipid content in crop seeds via conventional breeding or positive genetic regulation. Typically, the conventional breeding can only increase the specific content in crop seeds by 2˜3%, due to the limited genetic varieties in the sources. Specifically, the conventional breeding is carried out by selecting the desired properties among the mutants derived from random variations without being directed. The drawbacks of this method include randomness and the amount of time consumed in obtaining the genetic stability.
Positive sense genetic engineering can theoretically provide the possibility of directionally increasing the content of protein or lipid in crop seeds. However, being technically difficult to practice, it is far from the industrial application. In this connection, for example, the increment is limited, the expression patterns of the target genes in vivo are complex, and it is difficult to obtain the balance among the desired properties. Until now, there has been no success reported in this connection.
In the early 50's, it was found that the contents of proteins and lipids were inversely correlated to each other. Thereafter, in the 80's, it was found that, in soybeans, the protein content was positively related to the activity of the phosphoenopyruvate carboxylase (PEPCase)(Agri. Bio. Chem., 1989,53(3), ps. 885˜887). Actually, the biosynthesis of either protein or lipid takes the phosphoenopyruvate as the common substrate. The phosphoenopyruvate is one of the products in glycolysis. It can either be converted into oxaloacetic acid by the PEPCase, or pyruvate, by the pyruvate kinase. The former directly participates in the anabolism of protein. On the other hand, the latter is first converted into acetyl-CoA by pyruvate dehydrogenase and then into Malonyl-CoA by the acetyl-CoA carboxylase (ACCase), and finally participates in the anabolism of fatty acid in this form. Therefore, it is indicated that the relative activity of PEPCase to ACCase, or vice versa, controls the flow direction of the common substrate, phosphoenopyruvate and the ratio of proteins/lipids produced.
Accordingly, it is an object of the present invention to provide a method for controlling the ratio of proteins/lipids in the crop seeds. The method of the invention is more practicable, time saving and genetically stable. Another object of the present invention is to provide new crops improved in the productivity of oil/protein by the method of the invention.